1. Field of the Invention
The present invention relates to a position detecting device. More particularly, the present invention relates to a novel position detecting device to which a display function is added without reducing transmittance.
2. Description of the Related Art
There are various kinds of input devices for providing position information to a computer. Such input devices include a kind of position information input device called a “touch panel”. The touch panel is an input device for operating a computer and the like by touching a flat detection surface thereof with an input tool such as a finger, a dedicated stylus pen and the like. The touch panel is configured by superimposing a position detecting device for detecting an indicated position on a display region of a liquid crystal display device. In the touch panel, the position touched by the finger or the dedicated stylus pen is detected, the detected position is indicated in the screen, and an instruction is output to the computer.
A touch panel is widely used in PDAs (Personal Digital Assistant), ATMs (Automated Teller Machines), railway ticket-vending machines and the like.
Various kinds of positional information detection technologies can be applied to a touch panel. For example, there exist a resistance film type position detecting device which detects the position based on pressure change, an electrostatic capacity type position detecting device which detects the position based on capacitance change of a film on the flat detection surface, and the like. A related art is described in Japanese Unexamined Patent Application Publication No. 10-020992.
In many cases, an electrostatic capacity type position detecting device is used to configure the aforesaid touch panel, especially when the position detecting device is used to detect the position indicated by a finger. When combining the electrostatic capacity type position detecting device with the display device, the position detecting device is superimposed on the display device.
A new type of display device, an “electronic paper,” attracts much attention recently. In the electronic paper, darkness (between, for example, white and black) and/or color are controlled by applying a voltage to electrically-charged color powder. Since the electronic paper consumes less electrical power and can be made much thinner compared with the liquid crystal display device (which is widely used as the display device), electronic paper is becoming popular, particularly when used to display a still image, a text and the like.
There is a demand for adding other functions to an electronic paper. For example, it is desired that the electronic paper allows a note, a mark, or a label to be attached thereto, just like a normal paper. To obtain these functions, a possible method would be to superimpose an electrostatic capacity type position detecting device on an electronic paper in a similar manner to the aforesaid touch panel, so that the aforesaid functions can be added.
However, when a position detecting device, such as the electrostatic capacity type position detecting device, is superimposed on a display region of a display device, a plurality of transparent members will be superimposed on each other in the display region. As a result, transmittance of the display region would be reduced. Further, since a plurality of transparent members are superimposed on each other, thickness of the electronic paper would increase compared with an electronic paper having no aforesaid additional functions.
In view of the problems described above, one object of the present invention is to provide a position detecting device to which a display function is added without reducing transmittance and increasing thickness.